I. Field of the Invention
The present invention relates to solenoid valves. More specifically, the present invention relates to solenoid valves that have minimal power requirements.
II. Related Art
Valves are commonly used to control the flow of fluids in a hydraulic or pneumatic system. Valves are used to turn flow on or off, modulate flow or to direct flow along alternative paths. Two-port valves, for example, are used to turn flow on or off or to modulate the amount of flow past the valve. Valves with more than two ports typically have (a) either one pressure (inlet) port and multiple outlet ports, or (b) one outlet port and multiple inlet ports. In the first case, the valve is used to connect the inlet port to a selected output port to permit fluid to flow from the inlet to the selected outlet. In the second case, the valve is used to connect the outlet port to a selected input port to permit flow from the selected input port to the output port.
Solenoid valves have two main components, the valve and the solenoid. The solenoid is a helical coil of insulated wire in which an axial magnetic field is established by the flow of electric current through the coil. Many solenoid valves have a plunger and a spring arranged along the axial magnetic field produced by the solenoid. The spring biases the plunger toward a position which closes the valve. Application of current to the solenoid creates a magnetic field sufficient to overcome the force of the spring and open the valve.
A problem with solenoid valves known in the prior art is that a substantial amount of electrical current is required to overcome the force of the spring to move the plunger and then retain the plunger in the open position. This adds to the cost of operation and also makes solenoid valves unacceptable for use in a variety of environments. There is a real need for an efficient solenoid type valve which can operate at low power.